Electromagnetic phonograph recorder



Sept. 22, 1936. J. JOHNSON ELECTROMAGNETIC PHONOGRAPH RECORDER Original Filed Sept. 19', 1927 2 Sheets- -S het 1 I INVENTOR. flimfre Joima'on BY Sept. 22, 1936 v M. J. JOHNSON 2,054,980 ELECTROMAGNETIC PHONOGRAPH RECORDER Original Filed Sept. 19, 1927 2 Sheets-Sheet 2 INVENTOR. Manfred J. hi/27.9071 B v ORNEYf Patented Sept. 22, 1936 2,054,9 I I ELECTROMAGNETIC PHONOGRAPH RECORDER Manfred J; Johnson, Naugatuck, Conn., assignor' to Dictaphone Corporation; Bridgeport-,Conm,

a corporation of New York f Application September 19, 1927, Serial No. 220,574 Renewed August 5, 1935 23 Claims. (cl. 179-10041) This invention relates to improvements in systems for translating or converting electrical impulses into mechanical movements, and to improved means employedin suchsystems. In

a more specific aspect, the present invention is recorder of the present invention with a protecting cover therefor shown in section.

concerned with recording sounds electrically.

' The recording mechanism herein disclosedis of the type employing an electromagnet field A and a separately energizedor electrically controlled armature, the armature being connected to an air disturbing member such as a diaphragm 'or to a stylus adapted to record on a record blank. In order that the armature may have sufiicient amplitude movement to produce results under more or less adverse conditions, the electric recorder has interposed betweenvit and the sound sensitive device such as aflmicrophone, a'thermionic amplifier. fThis', briefly stated, refers to. the systems disclosed herein but, so far as some of the features of the present invention are concerned, namely the improved construction of the electrical recorder from a mechanical "point ofview, the present invention is not limited to electricaltranslating units used merely in this particular system.

Animportant' feature of..this.invention is the provision of an'electrical'recorder having a field magnetizing coil supplied by' a sourceof current used in an amplifying circuit connected with the'i'ecorder.

And a further and co-related feature is the arrangement of the field magnetizing coil so that it will act to by-pass the direct-current "component, of the current fed to the recorder, 3 around the armature actuating coil toprevent any tendency of the armature to become permanently magnetized orbiased toward one polarity, and yet so that it will not passvoice-currents but will force the latter to flow through the actuating coil. c

It will thus be seen that, according to the present invention, a single coilis arranged to function. both as a voice-frequencybhoke coil, andalso as a magnetizingcoil for the field of the device. This arrangement naturally tends to reduce the cost of the device and gives remarkable results. v

I Another feature of the presentinvention is" the provision of improved'mounting means for the 5' armature and improved'means for damping the oscillations of the armature so as to bring the amplitude of the vibrations within proper limits forithe successful functioning of the device. r 1 Other features and advantageswill'hereinafter 35 appear.

corder taken for the most part on the line 3--3 e I l the accompanying drawings- Figure l is a sideview, partly in section, of

phonograph showing the recording mechanism vof the present invention applied thereto.

Fig. 2 is a front elevation of. the electrical 5 Fig. 3'is a sectional view of the electrical reof Fig. 2. 10

Fig. 4 is a plan view of the electrical recorder showing the cover removed.

Fig. 5 is a disassembled perspective view showing some of the component parts of the electric recorder. 15

Fig. 6 is a diagrammatic view showing a system, according to the present invention, employing the electrical recorder shown in Figs. 1 to 5.

The phonograph shown inthe accompanying,, drawings comprises a base ID on which is sup-2' ported for rotary movement a mandrel H for a sound-record l2 over which moves a carriage l3 under the influence ofa feed-screw l4 driven concomitantly with the mandrel II and engaged v by a feed-nut I5 on the carriage. The carriage "25 usually supports a sound-box for recording and/or reproducing on a record blank or record,

and has-a socket l6 for receiving the sound-box.

In thepresent case, however, there is substituted for the usual sound-box, a sound-box '31) made in accordance with the present invention and comprising means for electrically recording desired sounds. This electric recorder, indicated generally by the reference numeral ll, comprises a base l8 in the form of a disk adapted to fit 35 in the socket l6 of the carriage I3. Pivotally mounted on a bracket carried by the base I8 is a lever 19 pivotally supporting at 20 a stylus lever 2i whichis ,a first-class lever having at one end a stylus '22 and at the other end pivotal 40 connection with an actuating link or rod 23. The pivotal mounting of the lever I9 is provided,

as usual, to permit thestylus to be raised clear of the record blank by manipulation of a;1ever A 24, alsoto permit gradual rise and fallofthe 4'5 stylus in accommodating itself to eccentricities of the record surface While the record isrotating, and also to accommodate itself to records of differentthicknesses or diameters. ,7 I

. The. stylus 22 is caused to'vibrate so as to .cut undulating helical grooves in the record surface corresponding-to sound vibrations by movements transmitted to it through the link 23 and armature 25 adapted to be controlled by an actuating 'coil'26'. The relation between the actuating coil 26 and the armature is substantially the same as that disclosed in the patent to Capps, No. 441,396, dated Nov. 25, 1890, and accordingly, the actuating coil has a central passage 21 through which the armature extends when the armature is placed in a magnetic circuit comprising polepieces 28 having pole-tips 29 and 30, the magnetic flux flowing through said magnetic circuit being supplied'by a perinanent'lnagnet'or by a magnetizing coil.

According to the present invention, the polepieces 28 are secured together so to e'ach'be the proper distance from the armature by means of a bridge plate 3| having holes 32 through which screws 33 pass and enter tapped holesin the pole-pieces 28. The bridge'plate 3[ is made of non-ferrous material and forms no part oi the magnetic circuit. Thebridge plate 3 ;l has an aperture 34 through which the armature25 extends. In order that it may beconveniently adjusted in its assembly so that it will lie midway between thepole-tips 29 and-'39 of each of the poles 28, the armature'is mounted onthe outside face of the bridge plate 3|. This mounting comprises a strip 35 of resilient material to whichthe end of the armature is riveted as at 35. The armature mounting strip '35 extends transversely with relation to the armature and at eachof its ends is provided with elongated slots 31' through which mounting screws 38 pass, see Fig. 2. These screws 38 are threaded'in the plate 3| and when loosened permit movement of the armature in the direction of thepole-tips 29 and 39 in the gap between' the latter. When the armature is properly positioned in the gap, the screws 39 are tightened to securely hold the armature in the desired position. The mounting'strip 35 is cut-away at 39 so as to decrease its resistance to torsional movement to that just ufficient to-maintain the armature in normal position-in the magnetic circuit. The armature being fulcrumed at one end on the supporting strip 35 is'provided at its other end, which protrudes beyond'the pole-pieces 28. with a connection 48 to the link 23- which is connecte'dwith the stylus lever 21.-

In order to keep the amplitude of vibrations of the armature 25 within proper limits for the successful operation of the device, making ita periodic, the present invention provides damping means operative upon the free end of the armature at a point adjacent its connection 40 to the link 23-. This clamping device, according to the present invention, comprises a pair of blocks M of rubber or other resilient material which are placed at opposite sides of the armature. These blocks 4! are held in operative position by angular pressure plates 42, one side of each of which is provided with an elongated slot 43 for the reception of a screw 44 threaded in the related pole-pieces 28. In assembling and'adjusting the device, the screws 44 are loosened and the pressure plates 42 are forcefully brought together so that they press with considerable force upon the armature and so that they press with equal force and permit the armature to maintain its centralized position in the gap between the facing pole-pieces 28. Movement of the pressure plates 42 for this purpose is permitted by the elongated slot 43 therein. When the plates have been properly adjusted and the rubber blocks 4l' are under tension and in proper position, the screws 44 are tightened to prevent accidental or unintentional movement thereof. Preferably, composition of the blocks ll is such that when the blocks are pressed against the armature with sufficient force, the side margins of the blocks touch each other, as shown in Fig. l, at both sides of the armature. Hence, the armature is confined entirely by the rubber blocks which then act as though the armature were inserted in a single block of rubber, which, however, is under tension.

If desired, the pole-pieces 28 may be held more rigidly by the addition of a U-shaped non-ferrous plate 45, one secured to each side of the two blocks 28 by'screws 46, see Fig. 1.

As stated above, magnetic flux applied to the pole-pieces 28 may be supplied, so far as some of the aspects of the present invention are concerned, from a permanent magnet or from an electromagnet having a magnetizing coil. It is pre ierredjfor reasons hereinafter given, to supply the magnetic flux by means of a magnetizing coil having a central aperture 48 through which a leg 49 of an angular field-piece 50 passes. The angular field 56 is screwed to the lowerblock 29, see Fig; 5, and then extends rearwardly where it is provided with the leg 49 which passes through the energizing coil 41. After the coilis placed on the leg 49, another arm 5| of the field-piece is secured to the leg 49 by screws 52 and holds the coil 41 in operative'position. The forward end of the arm 5| contacts 'with' the upper pole-pieces 28 to' which it is secured by screws '53. Thus, it will be seen that, there is provideda magnetic circuit including the lower pole-piece 28, field-piece 5|] having the'leg'49, and arm 5!, and'the' upper pole-piece 28, in thegap of which is located the armature '25.

Preferably, 'in manufacturing the device, first the'pole-pieces are secured to the bridge plate 3|, then the armature is put in'position and adjusted, the field is then completed by'assembling field-piece 59 and the field-piece arm 5| after placing the magnetizing coil 41 on the leg 49, then the assemblage is secured to the base I8 byscrews 54 '(as shown in' Fig. 3) and then the link 23 is passed through a clearance opening 55 in the field-piece 50, and finally the ends of the link are connected to the armature 25 and stylus lever 2|.

The entire device may 'be enclosed by a coyer 56 secured to posts 51 carried by-the base I8, and the cover may have an opening 58 through which thewiresleading to the unit may pass. Referring now to Fig; 6, which shows a system employing thefelectrical recorder of the present invention, sound from its original source impinges upon the microphone or the pick-up device 59having a local battery 69 in series with itandin' 's eries'withprimary 6] of an induction or coupling coil. The secondary 62 of the induction coil may, of course, be connected directly to the electrical recorder if so desired.

However, in order that soundswhich are feeble at the source may be recorded, it is preferable that the induction coil be connected atfone side We wire 63 tothe grid 64 ofa thermionic amplifier 65, whose filament or heating member is connected by wires 61 and 68 to a negativebias battery Cand from the latter by a wire 69 to the other side of the secondary 52. The fila- 'ment, as"usual, is connected by a wire 10 to a source A of current supply therefor which is connectedby a wire H to a rheostat 12 connected by a wire 13 to the wires61 and 68. The plate 14 of the thermionicdevice 65 is connectedby a' wire 15' to the electric recorder, the latter is =1 wouldretard travel of the carriage and soon -a'connectediby a wire 16 .to-a1 source of platevoltageisupply B which-in turn is conne'ctedxby a v Variations and" modifications may be made wire c'l'ltto the .wire6l leading to the filament.

So far as some'aspects of the present invenfor instancegby the source A for the filament.

1 However, according .::to the; present invention,

'the magnetizing coil ll-is. energized to cause pieces 28 bythe direct-current "component of magnetic fiux to flow through'the magnetic 'circuit comprising the field-pieces 50 "and polethe current flowing through the" plate circuit of rent supply B, the-wirel'l, wire 61, and the .the thermionic device. This circuit includes the plate 'I4,'the wire 15; the wire, source of 'curgizing coil for said armature disposed between 4 -spacef'between the filament 66 andt'he plate 14.

Accordingly, the coil'fl-is connected by a wire I "18 directly to' thewire 15 leading'to-the plate 14 and by -'a wire19 directly to the wire 16 2. A translating device comprising a magnetic leading' to the source-of current 3' Since the direct-current component-of the current pass- 'ing through the-platecircuitis usually'highfthe winding of the coil is adapted for thiscurrent, andthis winding and. the field-pieces 50 outwardly beyond' said "pole-pieces; and means and are'so proportionedthat the impedance of the coil to voice -currents is so high that the voice-currents pass through a course of less resistance and ultimately to the actuating coil field-piece; pole-pieces secured thereto in juxta- 26. For this purpose, the actuating coil'26 is connected by a wire 80' tothe wire 16 leading to the source of current-supplyB and the other one side of- 'a condenser 82, the other side of side of the coil 26 is connected by a wire 8! to which is connected by a wire 83 to the wire 15 leading to the plate 14; Consequently, the voicecurrents find'an easy path through the condenser and through the actuating coil back to the source of current-supply B, and because'of 'theinterposition of the condenser 82" between "-theplate I4 and the actuating'coil 26, the direct- "current component of a the currents flowing through the plate circuit cannot pass to the actuating coil 26, and hence pass through the coil 41 and causefthe latter to magnetize the field-piece BO and-the'pole-piecesiil. 7 Thus, it will be seen that the present invention provides a single coil which acts both asl-a choke coil f to'prevent the' direct-current component of the current flowing through the plate circuitfrom permanently magnetizing the armature'or biasing thearm'ature toward one polarity, and to magnetize the field piece for the "electrical recording unit. H a

The condenser 82,' described in connection j with the system shown in 'Fig. '6, may, of course, be located in proximity to the'thermionic amplitying device. However, it is preferable that the condenser be associated with the electrical recording unit and isso' shown in Figs. J1 to 4, m which the condenser 82 is 'secu'red to a; fibre plate 83 by screws 84, the plate being' securedto the arm 5| of the field 50 by a' screw 855 When the condenser is so located, a further advantageous result is obtained, forthen'only"two wires 'namely wires 15 andQld-needbebroughtto the 7 electrical recording unit through the opening 58 --''of the cover therefor? Thus, instead of having a cable of three {or more wires, which would be necessary in the event that an auxiliary source of current were utilized to magnetize the field, the present invention provides only two wires This is an important factor since -the carriage, as above stated, travels-from side to side'and any bulkycable which' might be used become worn due to friction within the scope of this invention and porti0ns of the improvements may be used without others.

an armature disposed between and extending outwardly beyond said pole-pieces; an enersaid pole-pieces'and means for mounting the v armature on the bridge plate for oscillatory movement said means being connected to one endofsaid armaturei' f field-piecei pole-pieces. secured thereto in juxtaposition; -a bridge plate of nonmagnetic material structurally connecting the pole-pieces; an armature; disposed between and extending- "foradjustably mounting the armature on the bridge platefor-oscillatory movement.

- 3Q A translating device comprising amagnetic position; a bridge plate of non-magnetic material "structurally connecting the-pole-pieces; an armature disposed between and extending outwardly beyond said pole-pieces; and a spring member riveted to theend of said armature and secured to said bridge plate for permitting oscillato'ry'movement of said armature about the axis of said spring member.

4; A-tr'anslating device comprising a magnetic field-piece; pole-pieces secured thereto in juxta- -position'; an "armature disposed between' said pole-piecesand extending outwardly beyond. said pole' pieces; an armature energizing coil 'mount'ed-between said pole-pieces; and means "supported at adjacent ends of said juxtaposed pole-pieces and adapted to engage the "portion of the armature extending beyond the polepieces to damp the vibratory movements of the armature, said means being each adjustable to f'perm'it the effect of each damping means to be varied at will.

5. A translating device comprising a magnetic fieldpiece; pole-pieces secured thereto in juxta- =posit1on; an armature disposed between said pole-pieces and extending'outwardly beyond the pole'-pieces;'- a bracket carried by each polepiece and disposed adjacent'the portion of the armature extending beyond thejpole-pieces; and

"blocks of resilient material interposed between the armature and the brackets.

6. A translating device comprising a magnetic field-piece; pole-pieces secured thereto in juxta- ='position; an armature disposed between said between said angle plate and'said armature to damp the vibration of' the'armature.

'7. A translating device comprising a'magnetic "field-piece: pole-pieces secured thereto in juxtaposition; a bridge-plate of non-magnetic material structurally connectingthe pole-pieces; an

: armature disposedbetween' said pole pieces and,"

extending outwardly beyond the pole-pieces; and a spring member having one end of said armature secured thereto, said spring member being secured to said bridge plate to permit oscillatory movement of said armature about an axis of said spring member.

8. A translating device comprising a magnetic field-piece; recessed pole-pieces secured thereto in juxtaposition; an armature comprising a magnetizable bar extending between and beyond said pole-pieces; a support for said armature; resilient means for securing an end of said armature to said support to permit oscillation of said armature between said pole-pieces; an energizing coil for said armature mounted within the recesses of, the pole-pieces, and an energizing coil for said field-piece.

9. A translating device comprising a magnetic field-piece; recessed pole-pieces secured thereto in juxtaposition; an armature comprising a 'magnetizable bar extending between and beyond said pole-pieces; a support for said armature; resilient means for securing an end of said armature to said support to permit oscillation of said armature between said pole-pieces; an

energizing coil for said armature mounted within the recesses of the pole-pieces; an energizing coil for said field-piece; and means supported at adjacent ends of said pole-pieces and adapted to engage a portion of the armature to damp the vibratory movements thereof.

10. A translating device comprising a magnetic field-piece; pole-pieces secured thereto in juxtaposition; a bridge plate of non-magnetic material structurally connecting the pole-pieces; an armature disposed between said pole-pieces and extending outwardly beyond the bridge plate; means for adjustably mounting the armature on the bridge plate for oscillatory movement; and means supported on adjacent ends of said pole-pieces and adapted to engage the portion of the armature extending beyond the polepie'ces to damp the vibratory movements of the armature, said means being each adjustable to permit the eifect of each damping means to be varied at will.

11. An electrical sound recorder comprising, in combination, a frame, a floating support pivetally mounted on said frame,- a lever arm pivotally mounted. for oscillation on said floating support, a stylus mounted on one end of said arm, a link pivotally secured to the other end of said arm, a magnetic driving motor mounted on said frame and comprising a vibratile armature biased to neutral position, and electromagnetic means for positively actuating said armature in either direction, and a connection between said armature and said link,

12. An electrical sound recorder comprising, in combination, a frame, a magnet support secured to said frame, a magnetic driving motor positioned on said frame, said motor comprising a vibratile armature, spring-biased to neutral position, and electromagnetic means for positively actuating said armature in either direction from neutral, a floating support pivotally secured to said frame, a lever mounted for oscillation thereon, a stylus mounted on one end of said lever, and a link pivotally connected on one end to the other end of said lever, and connected at the other end to said armature.

13. An electrical sound recorder comprising, in combination, a frame, a magnetic driving motor positioned on said frame, said motor comprising a vibratile armature, aspring for supporting said armature in neutral position, and electromagnetic means .for positively actuating said armature in either direction from neutral position, a floating support pivotally secured to said a stylus on one end of said lever, and a rigid link pivotally connected between one endv of said armature and-the end of said lever opposite said stylus, said linkv being so arranged as to positively drive said stylus in either direction ofmovement. t

14. An electrical sound recorder comprising,- in combination, a frame, a magnetic driving motor positioned on saidframe, said motor comprising a magnet having pole-pieces extending toward each other, and each having projecting portions at each end defininga winding-receiving space, a winding therein, an armature positioned between said pole-pieces and interlinking said winding, 2, spring for supporting said armature in neutral position for oscillation, anddamping means interposed between said armature and said pole -pieces at the point of maximum vibration amplitude of said armature.

15. An electrical sound recorder comprising, in combination, a frame,- a floating support pivotally mounted on said frame, a lever arm pivotally mounted for oscillation on said floating support, a stylus mounted on one end of said arm, a link pivotally'secured to the other end of said arm, a magnetic driving motor mounted on said fra-meand comprising a vibratile armature biased to neutral position, a magnet having polepieces defining a pair of air gaps at opposite ends of said armature, a coil surrounding said armature, and a connection between said link and said armature in the plane of said air gaps.

16. An electrical sound recorder comprising, in combination, a frame, a floating support pivotally mounted on said frame, a lever arm pivotally mounted for oscillation on saidfloating support about an axis parallel to the axis of said support but offset therefrom, a stylus mounted on the end of said lever arm remote from the axis of said support, a magnetic driving motor, mounted on said frameand comprising a magnet having a pair of pole-pieces defining an air gap, an armature of magnetic material mounted for vibration within said air gap, and a connection between said armature and the free end of said lever arm.

17. An electrical sound reproducer comprising, in combination, a frame, a floating support pivotally mounted on said frame, a lever arm pivotally mounted for oscillation on" said floating.

support, a stylus mounted on one end of said arm, and means for converting movements of frame, a. lever mounted for oscillation thereon;

said stylus into electrical currents, comprising a a magnet having pole-pieces defining a plurality of air gaps, an armature positioned within said gaps forvibration therein, a coil surrounding said armature, r and a connection between the free end 01 said lever arm and said armature.

18. An electrical sound reproducer comprising,

in combination, a frame, a floating support pivotally mounted on said frame, a lever arm pivotally mounted for oscillation on said floating support about an axis parallel to the axis of said support but offset therefrom, a stylus mounted onone end of said lever, and means for converting movements of said stylus into electrical currents, comprising a magnet having polepieces defining a pair of air gaps, an armature biased to neutral position andmounted for vibration within said gaps, and a connection be-;

tween the free end of said lever arm and said armature.

19. An electro-mechanical translating device comprising, in combination, a frame, a floating support pivotally mounted on said frame, a lever arm pivotally mounted on said support for oscillation thereon, a stylus mounted on one end of said arm, a magnet mounted on said frame, pole-pieces defining an air gap mounted on said magnet, an armature mounted for vibration in said gap and biased to neutral position, and a connection between said lever and said armature.

20. An electro-mechanical translating device comprising, in combination, a frame, a floating support pivotally mounted below said frame, a lever arm pivotally mounted on said support for oscillation thereon, a stylus mounted on one end of said arm, a magnet mounted on said frame,

pole-pieces defining a pair of air gaps mounted on said magnet, an armature mounted for vibration in said air gaps, resilient damping means surrounding a portion of said armature, and a connection between said lever and said armature.

21. An electro-mechanical translating device comprising, in combination, a frame, a floating support pivotally mounted below said frame, a lever arm pivotally mounted on said support for oscillation thereon,a stylus mounted on one end of said arm, a magnet mounted on said frame, pole-pieces defining a pair of air gaps mounted on said magnet, an armature mounted for vibration in said air gaps, resilient damping means surrounding a portion of said armature, and a connection between said lever and said armature at a point outside the portion thereof included between said air gaps.

22. A translating device comprising a magnetic field-piece; pole-pieces secured thereto in juxtaposition; an armature disposed between said pole-pieces; an energizing coil for said armature disposed between said pole-pieces; and torsional means connected to one end of said armature for supporting the armature in position for oscillatory movement between the polepieces.

23. A translating device comprising a magnetic field-piece; pole-pieces secured thereto 'in juxtaposition; an armature comprising a magnetizable bar extending between and beyond said pole-pieces; an energizing c'oil for said armature mounted between the pole-pieces; and resilient means secured to an end of said armature and mounted to retain said armature in position to oscillate between said pole-pieces.

' MANFRED J. JOHNSON. 

